1. Field of the Invention
The present invention relates to a brazing-filler material for joining a diamond and a metal and to a brazing method using the brazing-filler material.
2. Description of the Related Art
In diamond accessories, diamond tools, ceramic tools, etc., in plenty of cases, diamonds or ceramics are used being joined to substrates currently made of metal, such as plinth and shank. A silver-copper eutectic brazing-filler material containing titanium is used for the joining. The silver-copper eutectic brazing-filler material containing titanium is called TiCuSil, and titanium foil disperses to form fragment in a shape of flakes in an alloy having a eutectic composition of silver-copper. Diamonds or ceramics brazed to a substrate by the silver-copper eutectic brazing-filler material have a higher strength as compared with those joined by adhesives etc.
In diamonds bonded to a metal substrate using TiCuSil brazing-filler material, it is known that brazed interfaces of the diamonds provide black coloring. Since the brazed interface showing black can be observed through upper surface of the diamond, the TiCuSil material is not preferable for accessories. However, most coloring has been ignored in the case where ceramics had been joined by TiCuSil.
When a diamond is joined by TiCuSil, titanium in the brazing-filler material reacts with carbon in the diamond to form titanium carbide, and the titanium carbide existing between the diamond and the brazing-filler material bonds the diamond with the brazing-filler material. It became clear that, when titanium carbide is formed, irregularity is caused on the diamond surface, and thereby light was scattered on it, and the joined interface of the diamond provided black coloring.
And, the TiCuSil brazing-filler material is widely used also in manufacturing diamond tools, and it is known that the brazing-filler material occasionally provides a low joining strength. When metal works are processed using a tool having low joining strength, diamonds are sometimes removed from the tool to give contact between metal works and a shank, and both of the product and the tool might receive damage. Even if a low joining strength happens to be formed between diamonds and shanks, the defect has been considered to be caused by unskilled brazing technique without sufficient pursuit of cause.